Does Growth Hormone Treatment Alter Skeletal Muscle Mitochondrial Respiration in Rats?

Objective: Growth hormone (GH) has been shown to stimulate lipolysis and enhance lipid oxidation. We investigated whether GH could improve mitochondrial oxidative capacity. Method: Fourteen male Wistar rats received 14-day treatment with biosynthetic human GH (10 IU/kg/24 h) or placebo. Mitochondria were isolated from the total muscle of one hind limb of the rat. Mitochondrial oxygen consumption was measured in vitro using a Clark-type electrode with three substrates: palmitoyl-L-carnitine, pyruvate and succinate (+ rotenone). Results: Muscle mitochondrial yield was not significantly different in the GH-treated group from that in controls. Neither the basal nor ADP-stimulated respiratory state reached a significant difference between the 2 groups with palmitoyl-L-carnitine, pyruvate, and succinate. Conclusion: GH treatment did not improve the oxidative capacity of skeletal muscle mitochondria.